a. Field of the Invention
The invention relates to a method and system for near-field spectroscopy using targeted deposition of nanoparticles. In particular, the invention relates to a method and system for near-field spectroscopy using targeted surface enhanced Raman scattering (SERS) and surface enhanced infrared absorption (SEIRA) localized on deposited nanoparticles from an atomic force microscope (AFM) tip.
b. Background Art
The coupling of scanning probe microscopy with vibrational spectroscopy has been driven by the need to chemically analyze nano-structured devices and materials. This has been pursued from several directions that include near-field scanning optical microscopy (NSOM) and related apertureless methods where surface enhanced Raman scattering (SERS) is localized at the tip of a scanning probe microscope. The plasmon resonance mediated SERS effect can provide extraordinary signal enhancements, and when coupled with electronic resonance, single molecule sensitivity. Known methods and systems incorporate the SERS and atomic force microscopy (AFM) using specially metalized tips with better than 50 nm (nanometer) spatial resolution. In practice, this requires the integration of the Raman spectrometer to AFM and fabrication of specialized SERS active probe tips. There are limitations due to damage or contamination of the tip and the ability to track the tip during long integration times needed for spectroscopic measurements. With tip-based Raman AFM systems and methods, high numerical aperture optics is difficult to incorporate while maintaining sample flexibility. There is also a drift in the tip position from the target during the long spectral integration times that compromise the spatial resolution. These limitations can cause increased complexity in obtaining spectrochemical information from nanometer-scale regions on a surface.
Accordingly, there is a need for a method and system for near-field spectroscopy using targeted deposition of nanoparticles that does not have the problems associated with known methods and systems.